This Phase I SBIR application entitled "Substance Abuse Continuing Care through Mobile Assessment and Messaging" is designed to create a low cost, continuous care decision support text messaging intervention to increase treatment adherence, decrease drop-out and prevent the recurrence of problem drug use during and following professionally facilitated addiction treatment. Based on the high drop-out rates during treatment and relapse rates following treatment, it has been proposed that addiction should be treated similarly to other chronic illnesses that require long-term intensive monitoring and care. Recent research on adaptive phone-based continuing care interventions supports the use of a chronic care addictions treatment model both for those attempting to change illicit substance abuse and society as a whole. There is an emerging literature on the use of text messaging and ecological momentary assessment through mobile phones for low cost automated disease management of chronic illnesses like asthma and diabetes. Text messaging is ideally suited to addiction continuous care because the mobile phone is capable of providing low cost adaptive monitoring and feedback wherever and whenever relapse is most likely to occur. The proposed study is designed to develop the content, structure, programming and user interface of an automated interactive drug treatment continuous care text messaging intervention that can be modulated by the severity of symptoms during and following substance abuse treatment. The intervention will include web-based assessment, ecological momentary assessment (EMA), adaptive supportive messaging based on assessment results and counselor/social network alerts. The intervention is designed to both retain persons in treatment and help them sustain long-term change following treatment. We will obtain outside feedback and review of the preliminary intervention through focus groups with a heterogeneous group of clients enrolled in substance abuse treatment. Thought leaders with expertise in addiction, continuous care, text messaging and ecological momentary assessment will help develop the core content and features of the intervention. Specific content and programming benchmarks for success will determine Phase II feasibility. If successful this messaging program has the potential to significantly improve outcomes for the 2.2 million chronic illicit substance users who seek treatment each year without the financial burden and/or time commitment needed to implement traditional counselor based continuing care interventions. Additionally, the program can be used by clients of private addiction specialists and could be adapted to reach substance abusers in earlier stages of change as a stepped care intervention.